Add a namespace to the `csv_download_path` to fix job token auth logs Download CSV button

Related: #505728 (closed)

What does this MR do and why?

With the recent addition of Job token authentication log, you can now download a CSV containing a list of projects that have used a CI job token to authenticate to the project, and when they last did so.

In a project's Settings > CI/CD > Job token permissions > Authentication log, there's a Download CSV button. The URL generated for this button is malformed.

This MR - adds a namespace to the routing path and fixes the button URL.

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